1. Field of the Invention
The present invention relates generally to a container having a base structure for enhancing the structural integrity of the container.
2. Related Art
The warehouse club industry and consumer bulk purchasing have led to a boom in larger size packaging. Many liquid products are now sold to the consuming public in plastic containers that can be as large as 128 fluid ounces (one gallon). Larger containers that hold heavy fluids, including beverages, home products, motor oil, or the like, require a base structure that can withstand the forces applied against it, such as the weight of the fluid itself. Additionally, the containers must withstand rough handling during transportation and other forces applied to them as a result of being stacked during storage or from being dropped. Finally, large beverage containers that are filled by the so-called hot-fill process must be structurally sound to withstand various forces relating to the hot-fill process.
The hot-fill process is the procedure by which containers are filled with a beverage at a high temperature and capped soon thereafter. As the beverage cools within the container, stresses and strains develop in the container due to changes in the volume of the contents. In the case of large containers, the hot-fill process can cause, among other things, sagging in the base and rolls in the corners of the container.
A container that is commonly used in the hot-fill process is the polyolefin continuous extrusion blow-molded container. Polyolefin continuous extrusion blow-molded container's are multi-layer containers that provide the requisite structure and barriers to oxygen and oils, for example. These multi-layered containers typically include an exterior layer of polyolefin, such as, polypropylene or polyethylene as the main structure providing layer. Other layers can include oxygen barrier layers, moisture barrier layers, and regrind layers to provide the necessary barrier structures, as well as, adhesion between the layers.
It is understood by a person having ordinary skill in the art that to form a polypolefin continuous extrusion blow-molded plastic container, a parison can be heated in an extruder, captured by a mold, and blown in the mold. Specifically, to form the cavity of the container, a parison can be extruded up into the mold and as the mold comes together, a pneumatic blow pin, for example, can pierce the parison and blow the parison up against the walls of the mold. The mold typically contains flash pockets above and below the cavity in the mold to capture the excess parison above and below the cavity. It can be understood by a person having ordinary skill in the art, that as the parison is blown inside the mold and captured in the flash pockets, portions of the parison must adhere together. Once the container is cooled, the excess flash can then be cut away from the container after being ejected from the mold.
The desire to provide structural integrity to large containers has resulted in the development of different techniques to design containers that have structurally sound bases. The introduction of different structural elements into the base of the container is known to improve the containers structural integrity. While these structural elements molded in the base's structure can afford structural integrity, they must also be able to withstand the forces of the hot-fill process.
Although the aforementioned structural elements may function satisfactorily for their intended purposes, there is a need for a large container having a base structure that can withstand the forces of the hot-fill process. The base structures should be capable of accommodating variations in volume of the containers' contents and changes of pressure and temperature. Furthermore, the base structure should be capable of being manufactured in conventional high-speed equipment.